Grover on SPARKLE

Abstract

AbstractQuantum computers that take advantage of quantum mechanics efficiently model and solve certain hard problems. In particular, quantum computers are considered a major threat to cryptography in the near future. In this current situation, analysis of quantum computer attacks on ciphers is a major way to evaluate the security of ciphers. Several studies of quantum circuits for block ciphers have been presented. However, quantum implementations for Authenticated Encryption with Associated Data (AEAD) are not actively studied.In this paper, we present a quantum implementation for authenticated ciphers of SPARKLE, a finalist candidate of the National Institute of Standards and Technology (NIST) Lightweight Cryptography (LWC) project. We apply various techniques for optimization by considering trade-off between qubits and gates/depth in quantum computers. Based on proposed quantum circuit, we estimate the cost of applying key search using Grover’s algorithm, which degrades the security of symmetric key ciphers. Afterward, we further explore the expected level of post-quantum security for SPARKLE on the basis of post-quantum security requirements of NIST.KeywordsQuantum computerGrover algorithmLightweight block cipherSPARKLEAuthenticated Encryption with Associated Data